JPH05134466A - Electrophotographic developing method - Google Patents

Abstract

PURPOSE:To obtain a bright image high in image density and drastically small in fogging with excellent charge stability and to give a good image having sail image defect by grazing of a magnetic brush and excellent durability to a latent image supporting member, which is enhanced in transfer efficiency of the toner and uses an organic photoconductor small in surface hardness. CONSTITUTION:In the electrophotographic developing method, in which the organic photoconductor is used as the electrostatic latent image supporting member and an electrostatic latent developer containing the carrier and the toner is used, a carrier made by applying the resin, containing a copolymer of vinylidene chloride and at least one kind of monomer having an unsaturated double bond possible to copolymerize with vinylidene chloride, at least on a part of the core material is used as the carrier and development is executed by the magnetic brush developing method. The carrier coated layer is excellent in film strength and in adhesive strength with the core material and gives excellent durability, fast rising of chargeability and high chargeability to the carrier.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrophotographic developing method. More specifically, the present invention relates to an electrophotographic developing method having extremely excellent durability.

[0002]

2. Description of the Related Art Electrophotographic technology has been widely used and applied not only in the field of copying machines but also in the field of various printers in recent years because of its ability to obtain instant images and high quality images. For the latent image holding member, which is the core of electrophotographic technology, inorganic photoconductor materials such as selenium, arsenic-selenium alloy, cadmium sulfide, zinc oxide, and amorphous silicon have been conventionally used as the photoconductive material. However, recently, various organic photoconductor substances which are non-polluting and are advantageous in film-forming property and productivity have been developed. Among the organic latent image holding members, so-called laminated organic latent image holding members, in which a charge generation layer and a charge transport layer are laminated, have been widely put to practical use because of their high sensitivity and long life.

On the other hand, as for the developer, in the conventional two-component developer comprising a positively chargeable toner and a negatively chargeable resin-coated carrier, the resin for coating the carrier is vinylidene fluoride and tetrafluoroethylene. Polymers, fluororesin-based ones such as fluoroalkyl methacrylate copolymers, and silicone resin-based ones have been proposed (for example, JP-A-61-217068, JP-A-62-24268, and JP-A-2-26268). 96770, etc.).

Further, JP-A-53-92134 discloses that
It has been proposed to coat the surface of the carrier with a chlorinated or brominated vinyl-based copolymer, and vinylidene chloride is also exemplified as a monomer of the copolymer. However, the technique specifically disclosed and used is only the cascade development using a carrier coated with a copolymer using vinyl chloride.

[0005]

Each of these resin-coated carriers has merits and demerits. For example, fluororesin-based carriers have good chargeability, but have drawbacks in charge stability and adhesion to the core material. In addition, it is known that the silicone resin type has poor adhesion to the core material and has a drawback of gradually peeling, and therefore the copied image is not stable and gradually stains on white background (hereinafter referred to as fog). ) Becomes stronger, and all of them have the drawback of lacking durability.

Further, as a developing method, a cascade method or the like has been conventionally used, but it is difficult to miniaturize the apparatus, and a toner scattering and an edge effect, which is a phenomenon in which both ends of a thin line are darkened, are likely to adversely affect image quality. Due to such problems, the magnetic brush developing method is mainly used at present. In this magnetic brush developing method, when an organic latent image holding member is used, the surface hardness is smaller than that of an inorganic latent image holding member, so that a silicon resin resin, for example, is used as a carrier coating resin during magnetic brush development. As the number of actually photographed images increases, image defects due to scratches on the magnetic brush increase. In particular, all have drawbacks such as lack of durability, such as a marked increase in streak-like defects in a halftone image.

The inventors of the present invention have conducted extensive studies in order to solve the above-mentioned problems of the prior art, and as a result, in particular, coat a copolymer obtained by copolymerizing vinylidene chloride with another monomer. The above-mentioned carrier remarkably improves the above-mentioned defects and exhibits excellent characteristics. With this coated carrier, a clear image with extremely few fog and image defects can be obtained, and further, the transfer efficiency of the toner of the image can be enhanced. The inventors have found that and reached the present invention.

[0008]

That is, the gist of the present invention is as follows.
In an electrophotographic development method using an organic photoconductor as an electrostatic latent image holding member and an electrostatic latent image developer containing a carrier and a toner, vinylidene chloride and an unsaturated double copolymerizable therewith are used as a carrier. Electrophotographic development characterized by developing by magnetic brush development using a carrier obtained by coating at least a part of a core material with a resin system containing a copolymer with at least one monomer having a bond Exists in the law.

The present invention will be described in detail below. The electrostatic latent image holding member has a photoconductive layer provided on a conductive substrate. Examples of the conductive substrate include metals such as aluminum, iron, copper, brass, zinc, nickel, and stainless, or organic films, glass, conductive polymer materials, etc., which are made conductive by evaporating a metal film or the like. However, among them, aluminum is widely used, which is relatively inexpensive, lightweight, and has good workability. The form of the material is not limited as long as it is a conductive material, but a drum shape is preferable. Then, if necessary, a barrier layer for preventing charge injection from the substrate is provided.

Examples of the barrier layer include an aluminum anodic oxide coating, an inorganic layer such as aluminum oxide and aluminum hydroxide, polyvinyl alcohol, casein, polyvinylpyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide, Etc. organic layers are used. As the photoconductive layer provided on the substrate formed as described above, various organic photoconductive layers can be used, but in the case of using a laminated photoconductive layer including a charge generation layer and a charge transfer layer, Extremely useful.

As the photoconductor used for the charge generation layer, selenium and its alloys, arsenic-selenium, cadmium sulfide,
Various organic pigments such as zinc oxide and other inorganic photoconductors, phthalocyanines, azo, quinacridone, polycyclic quinones, perylene, indigo, benzimidazole and the like can be used. Among them, azo pigments such as monoazo, bisazo, trisazo and polyazo, metal-free phthalocyanines; coordination of metals such as copper, indium chloride, gallium chloride, tin, oxytitanium, zinc and vanadium, or oxides and chlorides thereof. The phthalocyanines mentioned above are preferred.

The charge generation layer is formed in a state where fine particles of these substances are dispersed in a binder. In the case of organic pigments, it may be a uniform layer of these substances. Examples of the binder resin used here include polyvinyl butyral, phenoxy resin, epoxy resin, polyester resin, acrylic resin, methacrylic resin, polyvinyl acetate, polyvinyl chloride, methyl cellulose, and polycarbonate resin. 20 to 300 parts by weight of the above-mentioned photoconductor is preferably contained in 100 parts by weight of the binder resin, and particularly preferably 30 to 150 parts by weight. The thickness of such a charge generation layer is usually 5 μm or less, preferably 0.01 to 1 μm.
m, more preferably 0.15 to 0.6 μm.

Various materials can be used as the charge transfer material used in the charge transfer layer. Examples include hydrazone derivatives, pyrazoline derivatives, heterocyclic derivatives such as carbazole, indole and oxadiazole, arylamine derivatives such as triphenylamine, stilbene derivatives, and polymer compounds having the above compound in the side chain or main chain. Be done. Among them, hydrazone derivatives, arylamines and stilbene derivatives are more preferable charge transfer materials. A binder resin is blended with these charge transfer materials as needed.

Preferred binder resins include vinyl polymers such as polymethylmethacrylate, polystyrene and polyvinyl chloride and their copolymers, polyarylate resins, urethanes, ureas, melamines, polycarbonates, polyesters, polysulfones, phenoxy resins and epoxy resins. , Silicone resins and the like, and partially cross-linked cured products thereof are also used. It is preferable to add 30 to 200 parts by weight, especially 50 to 150 parts by weight of the above charge transfer material to 100 parts by weight of the binder resin.

Further, the charge transfer layer may contain various additives such as an antioxidant and a sensitizer, if necessary. The thickness of the charge transfer layer is usually 10 to 40 μm, preferably 10
Used with a thickness of ~ 25 μm. As another example of the photoconductive layer, there is a dispersion type conductive layer obtained by dispersing the photoconductive particles as described above in a binder made of a binder resin and the charge transfer material. In this case, the total content of the photoconductor and the charge transfer material is preferably 20 to 200 parts by weight, particularly 40 to 200 parts by weight with respect to 100 parts by weight of the binder resin.
150 parts by weight is preferred.

In the present invention, an electrostatic latent image developer containing a carrier and toner is used. The carrier of the present invention coats at least a part of the core material with a resin system containing a copolymer of vinylidene chloride and at least one monomer having a vinylidene chloride copolymerizable unsaturated double bond. In particular, the copolymer is a binary copolymer composed of (a) vinylidene chloride and (b) acrylonitrile and / or acrylonitrile derivative, or (a), (b) and (c) It is preferably a multi-component copolymer composed of a monomer having an unsaturated double bond copolymerizable with.

Typical examples of the acrylonitrile derivative in the present invention include methacrylonitrile, that is, (b) acrylonitrile and / or acrylonitrile derivatives include acrylonitrile alone and methacrylonitrile alone, or Mixtures of acrylonitrile and methacrylonitrile in any ratio can be used.

The monomer (c) having an unsaturated double bond copolymerizable with vinylidene chloride or the like in the present invention is, for example, a styrene derivative such as styrene, α-methylstyrene or chloromethylstyrene (hereinafter the same. ); Methyl acrylate, ethyl acrylate, propyl acrylate,
Butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, 2-chloroethyl acrylate, α-fluoromethyl acrylate, α-fluoroacrylic acid ethyl, α-chloromethyl acrylate, methyl methacrylate, meta Α-substituted or unsubstituted alkyl (meth) acrylates such as ethyl acrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, octyl methacrylate, and 2-chloroethyl methacrylate; Vinyl ethers such as ethyl vinyl ether, 2-chloroethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, octyl vinyl ether, cyclohexyl vinyl ether and phenyl vinyl ether; vinyl acetate, vinyl chloride Vinyl acetates such as luacetate, vinyl butyrate, vinyl pivalate, vinyl benzoate; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, propyl vinyl ketone, butyl vinyl ketone, phenyl vinyl ketone; ethylene, propylene, isobutene, butadiene, isoprene, etc. Olefins; nitrogen-containing compounds such as N-vinylpyrrolidone, N-vinylcarbazole, 4-vinylpyridine and the like. These monomers can be used alone or as a mixture of two or more kinds.

In the present invention, the respective ratios of (a) vinylidene chloride to (b) acrylonitrile and / or acrylonitrile derivative and (c) a monomer copolymerizable therewith of the copolymer are (a) 70 ~ 30 mol%: (b) 2
0 to 60 mol%: (c) 0 to 40 mol% is preferable because the effects of the present invention are sufficiently exhibited. More preferably (a) 60 to 30 mol%: (b) 20 to 50 mol%:
(C) About 0 to 30 mol% is preferable. In the case of a binary copolymer, (a) 60 to 40 mol%: (b) 40 to 6
0 mol% is preferable. If the amount of vinylidene chloride is too much, it will be close to the properties of vinylidene chloride homopolymer, thermally unstable, and difficult to use because it will not dissolve in the majority of solvents, and even if it is used, the fluidity of the carrier will deteriorate. It is not preferable because it tends to adversely affect the copied image.
On the other hand, if the amount of vinylidene chloride is too small, the chargeability of the toner becomes insufficient and the copied image tends to be adversely affected. On the other hand, if the amount of the monomer (c) is too large, the charging stability is deteriorated and the copied image is adversely affected, which is not preferable.

In addition, the vinylidene chloride of the present invention and acrylonitrile and / or acrylonitrile derivative 2
Examples of commercially available resins contained in the terpolymer or the multicomponent copolymer include Saran Resin F- from Dow Chemical Company.
239, F-278 and F-310, Saran resin F-216, R-200, R-202 and R-2 of Asahi Kasei Corporation.
41B, Kureha Chemical Company's Kureharon Latex D0-81
8, D0-822 and D0-873S, Diofan A-690 manufactured by Mitsubishi Petrochemical Badisher, and the like.

The weight average molecular weight of the copolymer used in the present invention is usually 6 × 10 ^{4 to} 6 by the method of measurement by gel permeation chromatography (in terms of polystyrene).
0 × 10 ⁴ is preferable, more preferably 20 × 10 ⁴ to 40
It is about 10 ⁴ . If the weight average molecular weight is too low, the fluidity of the coated carrier deteriorates, which is not preferable. Also,
If the molecular weight is too high, there is no problem in terms of performance, but since the solubility in a solvent becomes poor, the coating process becomes complicated, which is not preferable.

As a method for producing the copolymer, a usual radical polymerization method is adopted, and bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization and the like are carried out. The coating material for the carrier core material may be used in the form of a composition obtained by blending the above copolymer with another resin or the like. More specifically, for example, vinylidene fluoride, a blend with a fluororesin such as vinylidene fluoride-ethylene tetrafluoride copolymer, a silicone resin, an acrylic resin, a polyester resin,
Polycarbonate resin, epoxy resin, phenoxy resin, polyamide resin, polyimide resin, urea resin, alkyd resin, phenol resin, vinyl chloride resin, polysulfone resin, polyether resin, polybutadiene resin,
Examples thereof include blends with other resins such as polystyrene resins and polyacrylonitrile resins, blends with silica powder, charge control agents, surfactants, lubricants and the like.
The amount of these blend materials used is preferably 50% or less of the copolymer. In order to prevent dehydrochlorination of the copolymer, stabilizers such as vinyl chloride and vinylidene chloride which are usually used for stabilization can be used. Examples of such stabilizers include metal soaps, epoxy compounds,
Examples include phosphite ester and polyol.

Further, as an application of the carrier of the present invention, a resin layer containing the vinylidene chloride-based copolymer of the present invention and another resin layer can be provided by forming the coating resin layer of the carrier into multiple layers. The film formation on the carrier core material is carried out in a manner substantially similar to the conventional method. For example, a copolymer used in the present invention or a mixture containing the copolymer and a blending material is dissolved or dispersed in an organic solvent to obtain a solid content concentration of 0.1 to 0.1.
A coating liquid of 30% by weight, more preferably 1 to 5% by weight, is prepared, and coated on a core material by a dipping method, a dry spray method, a fluidized spray method using a flow coater, and dried. If necessary, heat treatment may be performed at a temperature up to 100 ° C. after forming the film.

Any organic solvent can be used as long as it can dissolve the copolymer. For example, ketone solvents such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, and cyclohexanone; acetic ester solvents such as ethyl acetate, cellosolve acetate, n-butyl acetate; cyclic ethers such as tetrahydrofuran and dioxane. Examples thereof include aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as tetrachloroethylene, trichloroethylene and methylene chloride.

These solvents may be used alone or in admixture of two or more. Also, these solvents can be used as long as they have a boiling point of about 50 to 150 ° C., but from the viewpoint of dissolution treatment, drying treatment after coating, etc., 60
It is more preferably about 120 ° C.

As the core material of the carrier used in the present invention, all known core materials can be used and are not particularly limited. Specifically, ferrite, magnetite, and other metals exhibiting ferromagnetism such as iron, cobalt, and nickel; alloys or compounds containing these metals; not containing ferromagnetic metals, but exhibiting ferromagnetism by heat treatment. Examples of suitable alloys include, for example, so-called Whistler alloys such as Mn-Cu-Al and Mn-Cu-Sn: metal oxides such as CrO ₂ . The particle size of such a carrier is usually about 20 to 500 μm, more preferably about 30 to 200 μm.

The thickness of the coating layer of the carrier is
The thickness is preferably about 0.05 to 5 μm,
More preferably, it is about 3 μm. If it is less than 0.05 μm, the durability is not sufficient and the charging stability is deteriorated, which is not preferable. Even if the thickness of the coating layer exceeds 5 μm, there is substantially no problem in terms of performance, but the maximum value is reached in terms of performance, and the copolymer is consumed in large amounts, which is not economical.

As the carrier of the present invention, a resin system in which conductive fine particles are dispersed and contained in a resin system for coating a core material may be used. As the conductive fine particles, carbon black powder,
Graphite powder, Ti, Sn, Zn, Cu, Al, S
Fine particles of an inorganic substance selected from a wide range known in the art such as b, Fe, Ca, Mg, Si, etc. alone, alloys, or oxides or salts thereof are used. These may be used alone or in combination of two or more. The amount of conductive fine particles added to the coating resin is 0.05 w with respect to the resin.
t% to 20 wt%, preferably 0.1 wt% to 10 wt
% Is good. The particle size of the conductive fine particles is 2.0 μm or less, preferably 0.5 μm or less. When the conductive fine particles form an agglomerate, the above particle size refers to the particle size of the primary particles.

The carrier of the present invention is used as an electrostatic latent image developer in combination with a known toner, especially a positively chargeable toner. Such a toner is obtained by dispersing a colorant in a binder resin. Examples of the binder resin include styrenes such as styrene, valachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, Α-Methylene fatty acid monocarboxylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, lauryl methacrylate and 2-ethylhexyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile; Vinyl pyridines such as 2-vinyl pyridine and 4-vinyl pyridine; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl methyl ketone, vinyl ethyl metone, methyl isopropenyl ketone and the like Vinyl ketones; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene, and their halides: homopolymers of monomers such as halogenated unsaturated hydrocarbons such as chloroprene, and copolymers of two or more of these. Examples include polymers, and mixtures of two or more of these homopolymers and copolymers. Alternatively, a non-vinyl resin such as a rosin-modified phenol formalin resin, an oil-modified epoxy resin, a polyester resin, a polyurethane resin, a polyimide resin, a cellulose resin or a polyether resin, a mixture of these non-vinyl resins and the above vinyl-based resin, etc. Can be mentioned.

Examples of the colorant used in the toner include carbon black, nigrosine, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, methylene blue, rose bengal and phthalocyanine blue. The above toner may further contain or be mixed with additives such as waxes, silica and zinc stearate, if necessary.

The carrier of the present invention and such toner are
Usually, the so-called magnetic brush is prepared by mixing the former 100 parts by weight with the latter 0.3 to 20 parts by weight to form brush-like ears on a magnet roller and rub the surface of the electrostatic latent image holding member. Used in the development of electrostatic latent images of the method.

[0032]

INDUSTRIAL APPLICABILITY The carrier coating layer made of the copolymer or the composition containing the same used in the present invention has excellent film strength and good adhesion to the core material, and therefore not only has excellent durability. The chargeability rises quickly and gives the carrier high chargeability. Therefore, since the charging stability is excellent, a clear image with high image density and extremely little fog can be obtained, and the transfer efficiency of toner during image formation is increased.
Further, a latent image holding member using an organic photoconductor having a small surface hardness has few image defects due to scratches of a magnetic brush, and gives a good image excellent in durability especially in a halftone image.

[0033]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.
In the following, "part" means "part by weight". Example 1 10 parts by weight of a bisazo compound having the following structure was added to 150 parts by weight of 4-methoxy-4-methylpentanone-2, and pulverized and dispersed by a sand grind mill. The pigment dispersion liquid obtained here was used as polyvinyl butyral (manufactured by Denki Kagaku Kogyo KK, trade name # 6000-C) 5
% 1,2-dimethoxyethane solution, and finally a dispersion having a solid content concentration of 4.0% was prepared.

An aluminum cylinder having an outer diameter of 80 mm, a length of 348 mm, and a wall thickness of 1.0 mm, which has a mirror-finished surface, is dip-coated on the dispersion liquid thus obtained, and the dry film thickness is 0.4 g / m ^2. The charge generation layer was provided so that

[0035]

[Chemical 1]

Next, this aluminum cylinder was mixed with 95 parts by weight of the following hydrazone compound.

[0037]

[Chemical 2]

2.5 parts by weight of cyano compound

[0039]

[Chemical 3]

Below, 100 parts by weight of a polycarbonate resin (viscosity average molecular weight: about 30,000) shown below was mixed with dioxane.

[0041]

[Chemical 4]

After dip coating in a solution dissolved in a mixed solvent of tetrahydrofuran, 30 minutes at room temperature and 30 minutes at 125 ° C.
The layer was dried, and the charge-transporting layer was provided so that the film thickness after drying was 21 μm to prepare a laminated organic latent image holding member.

Next, a copolymer consisting of 54 mol% of vinylidene chloride and 46 mol% of acrylonitrile was produced, and gel permeation chromatography H, manufactured by Tosoh Corporation.
Column PL10 μm manufactured by Polymer Laboratories (UK) using LC-8020 with tetrahydrofuran as a solvent
The number average molecular weight distribution and the weight average molecular weight in terms of polystyrene were measured with two Mix (0.75φ × 30 cm). The molecular weight distribution is 6.5 × 10 ⁴ , and the weight average molecular weight is 32.8.
It was × 10 ⁴ (hereinafter, the molecular weight was similarly measured). The copolymer was dissolved in an equal amount of a mixed solvent of tetrahydrofuran and methyl ethyl ketone to give a solid content of 1.8.
% Coating solution, spherical spherical ferrite having an average particle size of 100 μm (DFC-150: manufactured by Dowa Iron Powder Co., Ltd.) was applied as a carrier core material by a fluidized spray method so that the dry film thickness was 2 μm. A coated carrier was obtained.

On the other hand, 100 parts of a copolymer resin of styrene and n-butyl acrylate, 5 parts of carbon black, 2 parts of low molecular weight polypropylene, a quaternary ammonium salt type charge control agent (trade name P-51 manufactured by Orient Chemical Co., Ltd.). Hydrophobic silica fine powder (manufactured by Degussa Co., trade name R-97) is used for 100 parts of a toner having an average particle diameter of 10 μm, which is composed of 2 parts of kneaded and pulverized product.
2) 0.1 part was added and mixed with a Henschel mixer to obtain a silica externally added toner. A developer was prepared by mixing 4 parts of the silica externally added toner with 100 parts of the resin-coated carrier. Subsequently, a commercially available copying machine equipped with the previously prepared organic latent image holding member and using a magnetic brush development method (SF manufactured by Sharp Corporation).
8800) was used to perform a live-copy durability test, and image density was measured, and fogging was determined and toner transfer rate was evaluated. As a result, a stable and clear image with little fogging was obtained. The toner transfer efficiency was also good. 1
There were almost no streaky image defects in the halftone image even after 100,000 copies were taken. The evaluation results are summarized in Table 1 below for each example.

Example 2 Copolymer consisting of 77 mol% of vinylidene chloride and 23 mol% of acrylonitrile (number average molecular weight distribution: 3.4 × 1)
0 ⁴ , weight average molecular weight 16.6 × 10 ⁴ ) was treated in the same manner as in Example 1 to produce a resin-coated carrier having a dry film thickness of 2 μm, and subsequently evaluated in the same manner as in Example 1,
A stable and clear image with little fog was obtained from beginning to end.
The toner transfer efficiency was also good. There were almost no streak-shaped image defects in the halftone image even after 10,000 copies were taken. However, the storage stability at 40 ° C. for 48 hours was slightly poor.

Example 3 Binary copolymer consisting of 25 mol% of vinylidene chloride and 75 mol% of acrylonitrile (number average molecular weight 6.6 × 1)
0 ⁴ , weight average molecular weight 30.3 × 10 ⁴ ) was dissolved in a mixed solvent of tetrahydrofuran / methylethylketone = 1/1 (Vol), treated in the same manner as in Example 1, and coated with a resin having a dry film thickness of 0.5 μm. When a carrier was manufactured and subsequently evaluated in the same manner as in Example 1, a stable and clear image with little fog was obtained from beginning to end. The toner transfer efficiency was also good. There were almost no streak-shaped image defects in the halftone image even after 10,000 copies were taken. However, the density after the actual copying of 10,000 sheets was slightly low, and there was some fog.

Example 4 Binary polymer consisting of 50 mol% of vinylidene chloride and 50 mol% of acrylonitrile (number average molecular weight 3.9 × 10 ⁴ ,
Weight average molecular weight 18.8 × 10 ⁴ ) was dissolved in a mixed solvent of methyl ethyl ketone / toluene = 65/35 (Vol) and treated in the same manner as in Example 1 to give a dry film thickness of 0.5 μm.
When the resin-coated carrier of 1 was manufactured and subsequently evaluated in the same manner as in Example 1, a stable and clear image with little fog was obtained from beginning to end. The toner transfer efficiency was also good. There were almost no streak-shaped image defects in the halftone image even after 10,000 copies were taken.

Example 5 Binary polymer (number average molecular weight 4.8 × 10 ⁴ , weight average molecular weight 23.50%) of vinylidene chloride 50 mol% and a mixture of acrylonitrile derivative 25 mol% acrylonitrile and methacrylonitrile 25 mol%. 5 x 1
0 ⁴ ) to methyl ethyl ketone / toluene = 65/35
When dissolved in a mixed solvent of (Vol) and treated in the same manner as in Example 1 to produce a resin-coated carrier having a dry film thickness of 0.5 μm, and subsequently evaluated in the same manner as in Example 1, it was stable from beginning to end. A clear image with less fog was obtained. The toner transfer efficiency was also good. There were almost no streak-shaped image defects in the halftone image even after 10,000 copies were taken.

Example 6 A resin-coated carrier was obtained in the same manner as in Example 1 except that spherical ferrite having an average particle diameter of 110 μ (FL100: manufactured by Powder Tech Co., Ltd.) was used as the carrier core material. After that, evaluation was performed in the same manner as in Example 1, and as a result, a stable and clear image with less fog was obtained from beginning to end. The toner transfer efficiency was also good. There were almost no streak-shaped image defects in the halftone image even after 10,000 copies were taken.

Example 7 A laminated organic latent image holding member was prepared in the same manner as in Example 1 except that the charge transport layer was provided so that the film thickness after drying was 35 μm. After that, the developer was adjusted in the same manner as in Example 1 and evaluated in the same manner as in Example 1. As a result, a stable and clear image with less fog was obtained from the beginning. The toner transfer efficiency was also good. There were almost no streak-shaped image defects in the halftone image even after 10,000 copies were taken.

Example 8 Copolymer consisting of 55 mol% of vinylidene chloride, 20 mol% of acrylonitrile and 25 mol% of methyl methacrylate (number average molecular weight: 4.6 × 10 ⁴ , weight average molecular weight: 3)
8.2 × 10 ⁴ ) was treated in the same manner as in Example 1 to produce a resin-coated carrier having a dry film thickness of 0.3 μm, and subsequently evaluated in the same manner as in Example 1 to show a stable and clear fog. Fewer images were obtained. The toner transfer efficiency was also good. There were almost no streak-shaped image defects in the halftone image even after 10,000 copies were taken.

Example 9 Copolymer consisting of 60 mol% of vinylidene chloride, 25 mol% of methacrylonitrile and 15 mol% of n-butyl acrylate (number average molecular weight 4.1 × 10 ⁴ , weight average molecular weight 2
8.7 × 10 ⁴ ) was treated in the same manner as in Example 1 to produce a resin-coated carrier having a dry film thickness of 2 μm, followed by Example 1
When evaluated in the same manner as above, a stable and clear image with less fog was obtained from beginning to end. The toner transfer efficiency was also good. There were almost no streak-shaped image defects in the halftone image even after 10,000 copies were taken.

Example 10 Copolymer consisting of 46 mol% of vinylidene chloride, 28 mol% of acrylonitrile and 26 mol% of methyl methacrylate (number average molecular weight 4.5 × 10 ⁴ , weight average molecular weight 38.
3 × 10 ⁴ ) was dissolved in an equal amount of a mixed solvent of tetrahydrofuran and toluene and treated in the same manner as in Example 1 to produce a resin-coated carrier having a dry film thickness of 1 μm, and subsequently evaluated in the same manner as in Example 1. As a result, a stable and clear image with less fog was obtained from beginning to end. The toner transfer efficiency was also good. There were almost no streak-shaped image defects in the halftone image even after 10,000 copies were taken.

Example 11 Copolymer consisting of 46 mol% of vinylidene chloride, 25 mol% of acrylonitrile, 28 mol% of methyl methacrylate and 1 mol% of acrylic acid (number average molecular weight 3.7 × 10 ⁴ , weight average molecular weight 26. 5 × 10 ⁴ ) was treated in the same manner as in Example 1 to produce a resin-coated carrier having a dry film thickness of 1 μm,
When subsequently evaluated in the same manner as in Example 1, a clear and stable image with less fog was obtained throughout. The toner transfer efficiency was also good. There were almost no streak-shaped image defects in the halftone image even after 10,000 copies were taken.

Comparative Example 1 A developer was prepared by using a spherical ferrite not coated with a resin as a carrier and a silica externally added toner in the same manner as in Example 1 and evaluated in the same manner as in Example 1 to obtain a copy. The image density decreased as the number of layers increased. In addition, the image was very dirty and dirty from the beginning. Further, the toner transfer efficiency was poor, and a large amount of untransferred toner was collected. After the actual copying of 10,000 sheets, streak-like defects were observed in the halftone image.

Comparative Example 2 Commercially available silicon resin coated carrier (core material is ferrite)
Was evaluated in the same manner as in Comparative Example 1 except that
The image density was almost good, but there was some fog and the image was slightly soiled. In addition, the amount of untransferred toner collected was slightly large, and the toner transfer efficiency was slightly poor. After the actual copying of 10,000 sheets, streak-like defects were observed in the halftone image.

Comparative Example 3 A developer was prepared in the same manner as in Example 1, and the organic latent image holding member prepared in the same manner as in Example 1 was subjected to cascade development to evaluate the image. It became an image. Furthermore, when cascade development was performed on the organic latent image holding member after 10,000 sheets were actually photographed and evaluated in Example 1,
A streak-like defect was observed in the halftone image, and an image with much fog was obtained.

[0058]

[Table 1]

Claims (2)

[Claims] 1. An electrophotographic developing method using an organic photoconductor as an electrostatic latent image holding member and an electrostatic latent image developer containing a carrier and a toner, wherein vinylidene chloride and vinylidene chloride are used as the carrier. Developed by magnetic brush development using a carrier in which at least a part of a core material is coated with a resin system containing a copolymer with at least one monomer having a copolymerizable unsaturated double bond. An electrophotographic developing method comprising: 2. The copolymer has a vinylidene chloride-acrylonitrile and / or acrylonitrile derivative copolymer, or vinylidene chloride-acrylonitrile and / or acrylonitrile derivative and an unsaturated double bond copolymerizable therewith. The electrophotographic developing method according to claim 1, wherein a carrier which is a multi-component copolymer with at least one kind of a monomer is used.